Various forms of underwater watercraft for recreational, exploratory and scientific use are known. Various arrangements of the known craft are known relating to providing a rider compartment and ingress/egress opening. Examples of such underwater craft are provided in U.S. Pat. Nos. 4,938,164, 5,704,309 and 6,321,676.
Some known underwater craft have a passenger compartment including a transparent sphere, in which a portion of the sphere is hinged, enabling ingress and egress. In such an arrangement, a ring seal may be provided, providing a fluid blocking seal between the exterior and interior of the compartment. Such a seal although low profile, can block a portion of the field of view from the interior of the compartment. For example, in one such arrangement, the ring seal is positioned approximately at an equatorial location on the compartment sphere. In another arrangement, such as in the Remora 2000 underwater watercraft from Comex, and the Triton 1000/3 craft from Triton LLC, a hatch is provided at a top end of the passenger compartment, blocking an upward portion of the field of view.
In another arrangement, such as in the Alicia craft, a spherical passenger compartment is provided, with the hatch positioned behind the spherical portion of the compartment. Such an arrangement avoids a view blocking seal, but also increases the size of the vehicle in a portion behind the seal in order to position the hatch.
It often is desired to load or unload passengers from an underwater craft while the craft is floating at the water surface, and to have the hatch above the surface so water does not flow into the interior while the hatch is open—as opposed to lifting the vehicle out of the water, such as using a crane. Various known craft, including those described above, retain a similar attitude on the surface as they do underwater, i.e. horizontal. In such known craft, ballast tanks are filled with air via pressurized tanks, to increase their buoyancy and retain the vehicle on the surface. In one such large watercraft, the Atlantis, the ballast tanks are positioned above the pressure hull where the occupants sit, affording stability.
Known single sphere submersibles have their center of gravity and center of buoyancy aligned along a vertical centerline of the sphere, aligning a hatch or ingress/egress opening with them. For surfacing where access is through a top hatch, to ensure that the submersible is in the similar horizontal attitude at surface as it is under water, the surface buoyancy would be spaced generally evenly in front and behind of the spherical cabin, for example in pontoons along either side, and usually at or below the horizontal centerline of the sphere. Likewise, heavy items, such as battery pods, are usually similarly equally placed in front of and behind the vertical centerline of the sphere. Positioning of the hatch or ingress/egress apparatus on or vertically above the passenger cabin has a disadvantage or reducing the field of view from the passenger cabin.
Accordingly, there is a need for an underwater craft having a wide or generally unobstructed forward, sideways and upwards field of view, providing an ingress and egress hatch to the exterior that is positioned out of the field off view, and also provides surface stability for ingress and egress, in addition to a reduced footprint enabling storage on smaller vessels and transport on smaller trailers.